The present invention relates to a switch and a portable device, and more particularly, to an engine starting switch and a portable device that are used in a smart key system for permitting an engine of an automobile to be started when the portable device is verified through communication between the portable device, which is carried by a driver, and an engine start controller, which is arranged in the automobile.
In recent years, smart key systems provided with a “smart ignition” function, which is described, for example, in Japanese Laid-Open Patent Publication No. 2002-029385, have been proposed for automobiles to improve their security level and convenience. When a portable device is carried into an automobile, a controller, which realizes the smart ignition function, permits starting of the engine when verifying that the portable device corresponds to the automobile. When the starting of the engine is permitted, a driver operates an engine starting switch to start the engine.
In more detail, a smart key system includes a portable device, which is carried by a driver, and an engine start controller, which is installed in an automobile. The portable device stores an ID code unique to the portable device (ID codes differ between portable devices). The engine start controller stores an ID code (ID code of the automobile), which is the same as that of the portable device.
In such a smart key system, the engine start controller transmits a request signal to a first area that includes substantially the entire passenger compartment of the automobile (normal control). In response to the request signal, the portable device transmits an ID code signal including an ID code. When receiving the ID code signal, the engine start controller determines whether the ID code of the portable device and the ID code of the automobile match. When the two ID codes match, that is, when portable device verification is achieved by communication between the portable device and the engine start controller in the first area based on the normal control, the smart ignition function is validated and the starting of the engine is permitted.
With the smart ignition function, the driver is not required to perform any complicated key operation to start the engine. The driver can start the engine simply by carrying the portable device into the automobile and operating the engine starting switch. In this way, the smart ignition function improves convenience. Further, the starting of the engine is not permitted unless the driver is carrying the portable device, which is far more difficult to duplicate than a conventional mechanical key. Thus, the smart ignition function improves security.
A portable device used for the smart ignition function includes a battery, which functions as a power source. When the battery of the portable device is drained, communication based on the normal control is not performed even if the driver carrying the portable device enters the first area (in the automobile). In this case, the smart ignition function is invalidated. Therefore, an “immobilizer function” is used instead of the smart ignition function when the battery of the portable device is drained. An immobilizer system provided with an immobilizer function is capable of coping with battery drainage in the portable device. With the immobilizer function, the starting of the engine is permitted when the driver performs a predetermined operation using the portable device.
In more detail, the portable device includes a transponder. The transponder stores a transponder code unique to the transponder, or unique to the portable device (transponder codes differ between portable devices). The engine start controller stores a transponder code (transponder code of the automobile), which is the same as that of the portable device.
With the immobilizer system, the engine start controller transmits a transponder drive radio wave to a second area that is much smaller than the first area in the automobile (backup control). In response to the transponder drive radio wave, the portable device transmits a transponder code signal including the transponder code. When receiving the transponder code signal, the engine start controller determines whether the transponder code of the portable device and the transponder code of the automobile match. When the two transponder codes match, that is, when portable device verification is achieved by communication between the portable device and the engine start controller in the second area based on the backup control, the immobilizer function is validated and the starting of the engine is permitted.
As described above, when the smart ignition function is valid, the driver carries the portable device into the first area (into the automobile) (normal operation). Afterward, if portable device verification is achieved in the first area based on the normal control, the starting of the engine is permitted. When the smart ignition function is invalid, the driver holds the portable device in the second area, which is much smaller than the first area. Then, if portable device verification is achieved in the second area based on the backup control, the starting of the engine is permitted. Thus, to have the starting of the engine permitted, the driver is required to hold the portable device in the second area (e.g., the driver is required to hold the portable device over an instrument panel at a position to which the drive radio wave is transmitted).
However, the driver is usually unaware that the smart ignition function is invalid and that the portable device must be held at the designated position. Thus, there has been a demand for a mechanism that would prompt the driver to perform the necessary operation when the smart ignition function is invalid.